A mitochondrial gene involved in cytochrome c maturation (ccmC) is expressed as a precursor with a long NH2-terminal extension in sugar beet.
Extensive genome rearrangement is one of the major mechanisms of angiosperm mitochondrial evolution. As a by-product, some angiosperm mitochondrial genes exhibit divergent organization, but not all of these genes have been fully characterized. Sugar beet ccmC, which plays an important role in cytochrome c maturation, harbors a unique extended NH(2) terminal region of 277 amino acid residues (N-extension) instead of a conserved translational initiation codon. The 5' termini of two major RNA species were determined by primer extension analysis, which revealed that the larger transcript covered the entire N-extension. Nucleotide sequencing of the cDNA revealed that a total of 31 C-to-U RNA editing events occurred in the N-extension and the ccmC-homologous region (ccmC-core region), resulting in improvement of amino acid sequence conservation. Antiserum was raised against a synthetic peptide corresponding to the ccmC-core region and was used for protein gel blot analysis of sugar beet and radish mitochondrial proteins. The detected 29.5-kDa signal band is shared by sugar beet and radish. Two additional larger signal bands are exclusively detected from sugar beet. The largest signal band is also detected by anti-N-extension antiserum. Our results indicate that sugar beet ccmC is translated as a long precursor with N-extension.
Kitazaki
Kazuyoshi
K
Laboratory of Genetic Engineering, Research Faculty of Agriculture, Hokkaido University, Kita-ku, Sapporo 060-8589, Japan.
Nomoto
Yuta
Y
Aoshima
Akihiro
A
Mikami
Tetsuo
T
Kubo
Tomohiko
T
D001483:Base Sequence; D027461:Beta vulgaris / Q000235:genetics*; D017931:DNA Primers; D018506:Gene Expression Regulation, Plant; D050259:Genes, Mitochondrial; D017343:Genes, Plant; D008969:Molecular Sequence Data; D010455:Peptides / Q000032:analysis; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics*; D011498:Protein Precursors / Q000737:chemistry* / Q000235:genetics*; D017393:RNA Editing; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
D017931:DNA Primers; D010455:Peptides; D010940:Plant Proteins; D011498:Protein Precursors; D012333:RNA, Messenger